1. Field of the Invention
The present invention relates to power drive apparatuses, such as inverters and servo amplifiers, including switching devices for converting and outputting electric power. In particular, the present invention relates to a power drive apparatus, in which a filter is mountable, the filter serving to suppress the transmission of noise generated by the switching devices to an input power source.
2. Description of the Related Art
FIG. 7 is an exploded perspective view of a known separate-filter-type power drive apparatus.
In FIG. 7, the power drive apparatus includes a case 1, a main circuit board 2 received in the case 1 and provided with an input terminal block 3 and a power module including switching devices for converting and outputting power, and a heat-dissipating plate 4 disposed at the bottom of the case 1 and for dissipating heat generated by heat-generating parts such as the switching devices mounted on the main circuit board 2. A filter unit 6, which is provided with a filter circuit including a choke coil, capacitors, and the like, is fixed by screws 5 to the heat-dissipating plate 4 at the bottom thereof. Relay wires 12 are connected with a filter-output-terminal block 8 at filter-side terminals 12a of the relay wires 12 and are connected with the input terminal block 3 at drive-side terminals 12b of the relay wires 12, whereby the power drive apparatus and the filter unit 6 are connected to each other through the relay wires 12. Power-source wires 10 are connected with a filter-input-terminal block 7, whereby the filter unit 6 and a power source (not shown) are connected to each other through the power-source wires 10.
The power drive apparatus including the filter unit 6 thus assembled is installed by screws 9 in an installation location.
As shown in FIG. 8, in the known separate-filter-type power drive apparatus, the filter unit 6 is disposed between a power source 11 and the input terminal block 3, in which the filter unit 6 suppresses the transmission of noise to the power source 11 from the switching devices included in a power module 18 mounted on the main circuit board 2.
However, in the known separate-filter-type power drive apparatus, the power source 11 and the filter-input-terminal block 7 were connected by the power-source wires 10, and the filter-output-terminal block 8 and the input terminal block 3 were connected by the relay wires 12, whereby productivity was decreased due to wiring processes, and the relay wires 12 must be prepared for interconnection due to the configuration of the separate-filter-type. The unit could not be reduced in size because the filter unit 6 was separated, and a mounting space for the filter unit 6 was required to be prepared outside the power drive apparatus. Moreover, when the power drive apparatus is used without using the filter unit 6, the power-source wires 10 must be connected with the input terminal block 3, and when the power drive apparatus is used together with the filter unit 6, the power-source wires 10 must be reconnected with the filter-input-terminal block 7 and the relay wires 12 must be connected with the filter-output-terminal block 8 and the input terminal block 3. That is, wiring must be changed according to the use. In this case, the power drive apparatus must be changed in the position according to the use, because the direction of connection of the power-source wires 10 was different between the input-terminal block 3 and the filter-input-terminal block 7.
In order to overcome these problems of the separate-filter-type power drive apparatus, a filter-built-in-type power drive apparatus has been proposed.
As shown in FIG. 9, the filter-built-in-type power drive apparatus is provided with a filter circuit 13 including a choke coil 14, a capacitor 15, and the like mounted on a main circuit board 2. The main circuit board 2 is received in the case 1, thereby eliminating the filter unit 6 shown in FIG. 7.
Referring to FIG. 10, in the known filter-built-in-type power drive apparatus, the filter circuit 13 is provided between an input terminal block 3 and a power module 18, thereby suppressing the transmission of noise to a power source 11 from a switching device included in the power module 18.
However, the known filter-built-in-type power drive apparatus must always contain the filter circuit 13 whether it is necessary or not. Although in Europe the suppression of noise is required by regulations, no filter is occasionally used in other regions. Consequently, unnecessary filter circuit 13 was mounted on the power drive apparatus in that case; as a result, the cost of the power drive apparatus was increased by an unnecessary component.
A known power drive apparatus has been proposed in, for example, Japanese Unexamined Patent Application Publication No. 8-308250, in which a filter unit is mounted on the power drive apparatus by applying a particular structure to an input terminal block of the power drive apparatus.
FIG. 11 is a perspective view of a power drive apparatus including an input terminal block having the particular structure disclosed in, for example, Japanese Unexamined Patent Application Publication No. 8-308250. FIG. 12 is a sectional view of the power drive apparatus shown in FIG. 11, in which a filter unit is mounted.
A known power drive apparatus 301 is provided with heat-dissipating fins 311 at the bottom thereof, and a filter unit 303a is also provided with heat-dissipating fins 311a at the bottom thereof. An input terminal block 302 of the power drive apparatus 301 includes terminals R, S, and T connectable to a power source, terminals U, V, and W connectable to an external device, and a terminal G (grounding) connectable to the both sides. Each terminal of the input terminal block 302 is configured in a manner such that a pair of conductive flat springs 315 and 316 are supported, opposing to overlap each other, by an insulative member 313 at one end of each flat spring 315 or 316, and the flat spring 315 is fixed to the insulative member 313 by a screw 314 so that the flat spring 315 is pressed to make contact with the flat spring 316. The pair of flat springs 315 and 316 form a female terminal 305. The other end of the flat spring 316 is connected to an interconnecting pattern 317A of a substrate 317 included in the power drive apparatus 301.
A filter unit 303a includes female terminals 305a, male terminals 304a, a substrate 325a, and a common mode reactor 310a. The female terminals 305a are formed on an end of the substrate 325a, and the male terminals 304a are formed on the other end of the substrate 325a. Each of the female terminals 305a is constituted by a pair of conductive contact parts 322a and 322b, and an insulative member 321a for fixing the contact parts 322a and 322b.
A power-source wire 10 is electrically connected to the flat springs 315 which are pressed by the screws 314. When the male terminals 304a are not inserted between the flat springs 315 and 316, the flat springs 315 and 316 are connected with each other by being pressed by the screws 314. An electrical current from the power source is supplied inside the power drive apparatus 301 through the flat springs 315 and 316, and the interconnecting pattern 317A.
The filter unit 303a is mounted on the power drive apparatus 301 by inserting the male terminals 304a between the flat springs 315 and 316. As shown in FIG. 12, the electrical current from the power source is supplied inside the power drive apparatus 301 through the flat spring 315, the upper face of the male terminal 304a, an interconnecting pattern 324a formed on the upper surface of the substrate 325a, the contact parts 322a and 322b, an interconnecting pattern 324b formed on the lower surface of the substrate 325a, the common mode reactor 310a, an interconnecting pattern 324c formed on the lower surface of the substrate 325a, the lower face of the male terminal 304a, the flat spring 316, and the interconnecting pattern 317A.
In this case, the filter unit 303a is disposed between the input terminal block 302 and a power module including switching devices, thereby suppressing the transmission of noise from the switching devices to the power source.
However, in the known power drive apparatus, a space for mounting the filter unit 303a is required outside the power drive apparatus 301, whereby the overall size of the apparatus is increased, and manufacturing cost is increased because of the particular input terminal block 302.